The present invention generally relates to endoprosthesis devices, to a procedure for making same, and to the use thereof. More particularly, the invention relates to a generally tubular endoprosthesis that is radially expandable between a generally unexpanded insertion circumference and an expanded implantation circumference which is greater than the unexpanded insertion circumference. Included are a plurality of generally circumferential sections, one or more of which includes one or more expandable segments that are bendable members which are generally collapsed when the endoprosthesis is in its generally unexpanded insertion orientation and which are generally opened when the endoprosthesis is in its expanded implantation orientation.
Endoprostheses are known for treating stenoses, stricture, aneurysm conditions and the like. An endoprosthesis device of this type, which is at times referred to as a stent, is typically placed or implanted by a mechanical transluminal procedure. Often a device of this type is percutaneously implanted within the vascular system to reinforce collapsing, partially occluded, weakened or abnormally dilated localized sections of a blood vessel or the like. Stents of this type can also be used in the urinary tract, the bile tract, the intestinal tract and the like. When endoprostheses or stents are used to treat a stenosis condition, typically such is done in association with a dilation element such as an angioplasty balloon. In this instance, the dilation element or balloon device opens the constriction, and a stent or the like is positioned thereat in order to prevent or at least substantially slow re-formation of the stenosis.
One attribute of a stent is that it is radially compressible and expandable so that it will easily pass through a blood vessel or the like when collapsed and will expand to its implanted size after the stenosis, aneurysm or the like has been reached. It is also desirable that a stent be generally flexible throughout its length so that it is easily maneuverable through bends and curves of the blood vessel or the like. It is typically desirable that a stent or endoprosthesis have a substantial amount of open space so as to allow for endothelialization along its length, to minimize the foreign body response, and to minimize interference with collateral blood vessels and the like. While it is important that a stent or endoprosthesis lodge securely into place at the desired location, it can be advantageous to have a stent that is removable through a transluminal percutaneous procedure, should removal be needed.
Various currently known stent products have structures that are essentially coiled springs. When this type of spring stent is tightly coiled, its diameter is relatively small for insertion through a blood vessel or the like. When the coil is sprung or coiled more loosely, the stent assumes its expanded, implantation orientation. Maass et al U.S. Pat. No. 4,553,545 is illustrative of this type of coiled spring stent or endoprosthesis. Multihelix or braided stents are also known. Stents of this general type suffer from poor maneuverability, and they are relatively thick walled and three dimensional. They are also difficult to remove once implanted, and they may exhibit numerous exposed, relatively sharp or jagged ends. Palmaz U.S. Pat. No. 4,733,665 is representative of an expandable stent of this general type. Gianturco U.S. Pat. No. 4,580,568 illustrates a percutaneous endovascular stent formed of stainless steel wire that is arranged in a closed zig-zag pattern somewhat in the nature of a bookbinder spring. Such a structure is somewhat unsymmetrical, and it may be subject to reocclusion due to the very large open space that is typically present between the wires of this type of device. Another type of stent is known as a Statz stent, and it includes a hypodermic tube with longitudinal slots etched into its body. While such a device has a high ratio of unexpanded to expanded diameter, it is a comparatively rigid, sharp-edged device which is difficult to maneuver through a tortuous path and is not easily removed in a transluminal manner.
With many of these currently known stent structures, the axial length of the stent decreases as the circumference of the stent increases, which is typically a disadvantage. For example, any such length reduction must be taken into consideration in selecting proper stent sizing for a particular implantation procedure. Also, this attribute of many prior stents requires the passage through the blood vessel or the like of a stent which is longer than the length actually needed for the implantation procedure being performed. This is a particularly difficult problem for procedures in which the stent must be passed through a pathway having twists or turns, especially for a stent structure that is not easily bendable.
The present invention avoids the various deficiencies of these types of prior art structures and provides important and advantageous features of endoprostheses or stents and the use thereof. In summary, the endoprosthesis of this invention includes a plurality of generally circumferential sections that are generally adjacent to one another along their respective opposing generally circumferential edges. At least one of these generally circumferential sections has an expandable segment that imparts radial expandability to the generally circumferential section. The expandable segment is a bendable, elbow-like member that is bendable between a generally collapsed or closed orientation and a generally opened orientation and is capable of assuming bending orientations between one that is fully closed and one that is fully opened. By this structure, the endoprosthesis or stent has an unexpanded insertion circumference and an expanded implantation circumference, which is greater than the insertion circumference. In addition, this variation in circumference is achieved without substantially changing the axial length of the endoprosthesis or stent. The stent is made by a procedure that is relatively uncomplicated, and, generally speaking, the stent can be transluminally explanted if necessary.
It is a general object of the present invention to provide an improved radially expandable, axially extending endoprosthesis of the type that can be transluminally implanted.
Another object of the present invention is to provide an improved endoprosthesis or stent that can be constructed to have very large radial expansion capabilities.
Another object of this invention is to provide an improved radially expandable axially extending endoprosthesis that is extremely maneuverable and capable of moving through a tortuous path.
Another object of the present invention is to provide an improved radially expandable axially extending endoprosthesis that can, if desired, be transluminally explanted by means of, for example, a snare lead or catheter.
Another object of the present invention is to provide an improved radially expandable axially extending endoprosthesis which includes members that can be spaced apart or pointed in a manner that enhances lodging of the endoprosthesis at its implanted site.
Another object of the present invention is to provide an improved axially extending endoprosthesis that can be constructed in order to be radially expandable by an expanding member or balloon of a catheter device and/or can be radially expandable due to spring-like properties of the endoprosthesis.
Another object of this invention is to provide an improved procedure for making an axially extending and/or generally tubular endoprosthesis that is radially expandable.
Another object of the present invention is to provide an improved procedure and system for transluminally explanting an axially extending radially expandable endoprosthesis or stent.
Another object of the present invention is to provide an improved radially expandable endoprosthesis that substantially avoids the presentation of any frayed edges and that generally maintains its axial length throughout various radial expansion positions.
These and other objects, features and advantages of this invention will be clearly understood through a consideration of the following detailed description